English verb conjugation
MUST FAIL

Regular verb: fail - failed - failed

Affirmation

Simple form	V-ing form
I must fail you must fail he must fail we must fail you must fail they must fail	I must be failing you must be failing he must be failing we must be failing you must be failing they must be failing
Perfect	V-ing perfect
I must have failed you must have failed he must have failed we must have failed you must have failed they must have failed	I must have been failing you must have been failing he must have been failing we must have been failing you must have been failing they must have been failing

Negation

Simple form	V-ing form
I mustn't fail you mustn't fail he mustn't fail we mustn't fail you mustn't fail they mustn't fail	I mustn't be failing you mustn't be failing he mustn't be failing we mustn't be failing you mustn't be failing they mustn't be failing
Perfect	V-ing perfect
I mustn't have failed you mustn't have failed he mustn't have failed we mustn't have failed you mustn't have failed they mustn't have failed	I mustn't have been failing you mustn't have been failing he mustn't have been failing we mustn't have been failing you mustn't have been failing they mustn't have been failing

Interrogative form

Simple form	V-ing form
must I fail? must you fail? must he fail? must we fail? must you fail? must they fail?	must I be failing? must you be failing? must he be failing? must we be failing? must you be failing? must they be failing?
Perfect	V-ing perfect
must I have failed? must you have failed? must he have failed? must we have failed? must you have failed? must they have failed?	must I have been failing? must you have been failing? must he have been failing? must we have been failing? must you have been failing? must they have been failing?

Interro-negative form

Simple form	V-ing form
mustn't I fail? mustn't you fail? mustn't he fail? mustn't we fail? mustn't you fail? mustn't they fail?	mustn't I be failing? mustn't you be failing? mustn't he be failing? mustn't we be failing? mustn't you be failing? mustn't they be failing?
Perfect	V-ing perfect
mustn't I have failed? mustn't you have failed? mustn't he have failed? mustn't we have failed? mustn't you have failed? mustn't they have failed?	mustn't I have been failing? mustn't you have been failing? mustn't he have been failing? mustn't we have been failing? mustn't you have been failing? mustn't they have been failing?